ATO pump not strong enough?

[Ayman]

Hello

I recently set up a 20-gallon AIO tank with a Red Sea ATO, but the pump is failing to deliver water to the display. Despite the pump's 2.5-meter (8-foot) maximum head pressure and my stand being only 3 feet tall, the water is not moving.

Anyone advise on the potential cause or suggest a solution?

 

[Coral reefer]

Air lock?
Turn pump upside down while submerged. See if bubbles come out
Or blow down the tube it’s supposed to pump out of might work

 

[Ayman]

Thanks @Coral reefer will try that tonight